videocrop: skip the transforming caps process when the passthrough mode is set
videocrop: skip the transforming caps process when the passthrough mode is set

When the passthrough mode is set, the basetransform class tries to accommodate
a difference between input and output caps. This behavior causes
the reallocation of the output buffers, and discarding the physical buffers
used for zero-copy processing.
To avoid this problem, the transforming caps process shouldn't be performed.

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